To provide passenger compartment comfort, vehicles have the capability to heat or cool the passenger compartment. Conventional vehicles use waste heat from the engine as the sole source of heating for the passenger compartment. With the advent of Battery Electric Vehicles (BEV), there is no longer any waste heat available so that other means of heating the passenger compartment are required. A typical BEV may use an electric heater to warm the passenger compartment. Similarly, Hybrid Electric Vehicles (HEV) pose different problems because the engine may not always be running and generating waste heat for use by the heating system. Plug-in Hybrid Electric Vehicles (PHEV) compound this issue by running with the engine off for significant periods of time. In order to provide optimal fuel economy benefits, it is desired to heat the passenger compartment without having to rely solely on engine waste heat.